On Thu, 28 Mar 2002, Lucky Green wrote:
:Which brings me to an issue that I hope may be on-topic to this mailing
:list: I would like to be able to enforce that the keys my users can use
:to authenticate themselves to my sshd to be of a minimum size. Is there
:a config option to sshd that will reject user keys below a minimum size?
:I didn't see anything in the man pages or my first go through the code.
no config option, but this change will be in the next release:
RCS file: /usr/OpenBSD/cvs/src/usr.bin/ssh/auth-rsa.c,v
retrieving revision 1.53
retrieving revision 1.54
diff -u -r1.53 -r1.54
--- src/usr.bin/ssh/auth-rsa.c 2002/03/25 09:21:13 1.53
+++ src/usr.bin/ssh/auth-rsa.c 2002/03/26 23:13:03 1.54
@@ -14,7 +14,7 @@
*/
#include "includes.h"
-RCSID("$OpenBSD: auth-rsa.c,v 1.53 2002/03/25 09:21:13 markus Exp $");
+RCSID("$OpenBSD: auth-rsa.c,v 1.54 2002/03/26 23:13:03 markus Exp $");
#include <openssl/rsa.h>
#include <openssl/md5.h>
@@ -77,6 +77,13 @@
u_char buf[32], mdbuf[16];
MD5_CTX md;
int len;
+
+ /* don't allow short keys */
+ if (BN_num_bits(key->rsa->n) < 768) {
+ error("auth_rsa_verify_response: n too small: %d bits",
+ BN_num_bits(key->rsa->n));
+ return (0);
+ }
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
